1. Technical Field
The present invention relates to an image forming apparatus.
2. Related Art
As a method for reducing the cost of image forming apparatuses, there is known a method in which a driving source for a developing unit (hereinafter, referred to as “developing unit driving source”) is used in common with a driving source for toner dispense (hereinafter, referred to as “toner dispense driving source”). In recent years, according to various demands, it is a main trend for the image forming apparatuses to have the functionality of a high quality mode or a high productivity mode. There is also a case where plural processing speeds for an image forming operation (hereinafter, referred to as “process speed”) are present for each mode.
In a case in which the developing unit driving source is used in common with the toner dispense driving source, and vice versa, and plural process speeds are present, as described above, a toner dispense rate may vary depending on the process speeds. For this reason, it is important to control the toner density to correspond to the varied toner dispense rate. The term, toner dispense rate, refers to an amount of toner for a unit time, dispensed to the developing chamber by the driving of toner dispensing means.
Furthermore, in electrophotographic image forming apparatuses, in order for a developing unit to develop an electrostatic latent image formed on an image carrying member into a toner image, it is necessary to dispense toner to the developing unit by the amount consumed by development. In general, in the case of a developing unit that supplies a bi-component developer composed of toner and carrier onto a developing roll with the developer being agitated in a developing chamber, the developer (toner and carrier) is conveyed and agitated by the rotation of an auger for agitation (hereinafter, referred to as “agitating auger”) provided in the developing chamber. When dispensing toner to the developing chamber, toner is dispensed through a toner dispense path or a toner dispense chamber connected to the developing chamber of the developing unit by the driving of a toner dispensing motor.
In such kind of an image forming apparatus, in order to prevent image quality error (such as BCO, overlapping, or toner cloud) while stabilizing an image density, it is important to control a toner density in a developing chamber to be within an intended range.